This invention relates to a device for placing a valve on a can.
An aerosol dispenser, i.e. a container from which material in aerosol form is to be dispensed, typically comprises a can within which the material is contained and a dispensing valve which is mounted in the open upper end of the can. A typical process for producing an aerosol-containing dispenser will now be described, referring to an example where the material to be dispensed is a drug. It will be understood, however, that this is only an example and that the invention is equally applicable to any other product dispensed in aerosol form, and also to product dispensed in non-aerosol form.
In this typical process a drug and a propellant which is liquid at room temperature are introduced into a can mixed to form a slurry. This takes place at a filling station. The slurry-containing can then passes to a crimping station and as it does so a valve is placed on the open upper end of the can. At the crimping station the valve is crimped onto the can to provide an air-tight seal between the can and valve. The can and valve assembly then passes to a gasing station where a propellant which is different from the first mentioned propellant and which is a gas at room temperature is forced under pressure into the can through the valve.
The period of time when the can is between the filling station and the crimping station is normally short, particularly if the process is operating at high speed, and this creates problems as regards the placing of the valves on the cans.
FIG. 1 of the accompanying drawings shows schematically one way in which valve placement is carried out. The cans A travel from left to right as seen in the drawing, and valves B are fed by guide means (not shown) to the position indicated in FIG. 1. In this position the valve is inclined with respect to the horizontal and when it is struck by the leading upper edge of the can it tips as indicated by the curved arrow and falls onto the open upper end of the can with the valve stem C pointing vertically upward. There are, however, considerable problems with this approach. The precise position of the valve at the instant it is struck by the can is critical. The valve cannot be too high up or the can will not strike it at all, and it cannot be too low down as there is only a very small clearance, indicated by d in FIG. 1, between the upper edge of the can and the portion of the valve which, when the valve is placed on the can, is lowermost. If the can were to strike that portion the valve would not fall correctly on the can.
Other methods of placing valves onto cans have been tried, but none has been particularly successful, and it is an object of the present invention to provide an improved method of placing a valve on a can.